Hot-forming apparatuses for producing a press-hardened shaped component from a blank may be used, for example, to produce press-hardened shaped components for automobiles, such as vehicle doors, side-impact supports, a-pillars, or b-pillars.
As the starting material for producing such shaped components, use is commonly made of steel sheet in the form of what are termed metal blanks which are cut from a coil. The blanks are first heated in a furnace, usually in a continuous furnace, up to the austenitizing temperature of the steel, such that the lattice structure of the steel changes. Then, the heated blanks are fed to a pressing device in which the blanks are shaped. The pressing device generally has a cooling device such that the shaped material can be quickly cooled in the press. The rapid cooling causes the formation, in the shaped component, of a martensitic structure, which causes a hardening the shaped component.
Such a hot-forming apparatus is known for example from EP 2 233 593 B1. This hot-forming apparatus has a preheating device which preheats the steel sheet to an elevated temperature before it is fed to the furnace. For preheating, two heating plates are brought into contact with the steel sheet from above and from below. The heating plates are removed from the steel sheet, such that the latter can be introduced into the furnace.
The known apparatus has proven useful in practice. However, it has been observed that the blanks cut from the coil often have undesired deformations or unevennesses which worsen as a consequence of the heating in the furnace. The deformed blanks cannot be reworked and are obtained as rejects. With respect to the economic viability of such hot-forming apparatuses, it is however desirable to reduce the reject rate and to permit a higher-rate method sequence.